1. Field of the Invention
The present invention mainly relates to a general-purpose water-cooled four-cycle engine, and particularly relates to an improvement of a water-cooled four-cycle engine in which: an engine core including a cylinder block, a cylinder head and a first crankcase half body is formed as a unitary part cast integrally, the cylinder block including a cylinder bore, the cylinder head including a combustion chamber as well as an intake port and an exhaust port which are opened to the combustion chamber, the first crankcase half body including a half portion of a crank chamber; an engine main body includes the engine core, a second crankcase half body and a head cover, the second crankcase half body including a remaining half portion of the crank chamber and connected to the first crankcase half body, the head cover connected to the cylinder head and defining a valve-operation chamber between the head cover and the cylinder head; a crankshaft housed in the crank chamber is supported by the first and second crankcase half bodies; a camshaft housed in the valve-operation chamber is supported by the cylinder head; a water jacket including a cylinder jacket and a head jacket is formed in the engine core, the cylinder jacket surrounding the cylinder bore, and the head jacket communicating with the cylinder jacket and surrounding the combustion chamber; and a timing-belt chamber is provided in a side portion of the engine core, the timing-belt chamber being adjacent to the cylinder jacket across a partition wall integrated with the engine core, and the timing-belt chamber housing a timing belt which connects between the crankshaft and the camshaft.
2. Description of the Related Art
Such a water-cooled four-cycle engine is already known, as disclosed in Japanese Patent Application Laid-open No. 5-26099.
The water-cooled four-cycle engine disclosed in Japanese Patent Application Laid-open No. 5-26099 needs as many as three opening portions to form the water jacket by casting out, because: paired opening portions are provided in the respective two side surfaces of the cylinder block in order to form the cylinder jacket around the cylinder by casting out; and the other opening portion is provided in the upper surface of the cylinder head in order to form the head jacket around the combustion chamber by casting out. This makes the structure of the casing dies complicated, and entails higher costs. In addition, the engine needs three lid plates to water-tightly close these opening portions as well. This makes the number of components and the number of assembling steps large. This brings about a disadvantage that not only causes high costs but also makes it difficult to make the engine compact.